1. Field of the Invention
The present invention relates to growth regulators for gramineous weeds and a method for regulating the growth of gramineous weeds using the same.
2. Description of the Related Art
Previously, Japanese lawn grasses have been used in various fields such as parks, gardens, playgrounds, golf courses, and the like. In Japanese lawn grasses, however, the growth is arrested during winter and the leaves turn yellow, and therefore in recent years cool temperate grasses which grow up through the winter have been used in a variety of fields.
In cultivation and maintenance of lawn grasses, it is inevitable that weeds invade the lawn.
These weeds sometimes disturb the growth of lawn grasses, spoil the beauty of lawn, and have an influence on a sporting event. For example, when gramineous weeds such as annual bluegrass (Poa annua L.) and southern crabgrass (Digitaria ciliaris Koel.), invade and colonize in the green field of a golf course, those weeds form the ears on the green; in particular, the white ears of annual bluegrass (Poa annua L.) would spoil the scenery and have an influence on putting in golf.
As for a conventional method for weeding in turf, clipping of lawn grasses with a lawn mower has been employed in order to prevent the growth of annual weeds. For example, in a bent grass green of a golf course, frequent clippings of weeds with a lawn mower wither and kill most of the annual weeds, thereby suppressing the growth of weeds to a large degree. Annual bluegrass (Poa annua L.) and southern crabgrass (Digitaria ciliaris Koel.), however, do not result in dying by clipping with a lawn mower. In addition, a large number of seeds produced by the ear emergence of Annual bluegrass (Poa annua L.) and southern crabgrass (Digitaria ciliaris Koel.) buds and colonizes, thereby growing to strong noxious weeds in a lawn field.
On the other hand, since annual bluegrass (Poa annua L.) strongly resists clipping with a lawnmower as mentioned above, it is said that if no appearance of ear is developed, the annual bluegrass per se could be utilized as a lawn grass of high quality.
In recent years, a large number of herbicides have been developed in order to control grass weeds in turf, and in Japanese lawn grasses, it is practically possible to control weeds only without chemical injury to lawn grasses using existing herbicides.
On the contrary, the existing herbicides are not sufficient in the herbicidal activity or sometimes cause chemical injury for cool temperate Western lawn grasses such as bent grass. This indicates that they are not necessarily satisfactory herbicides in the present circumstance.
Alternatively, there are also reports of a method to take care of the growth of lawn grasses without any herbicides by regulating the growth of lawn grasses or weeds using a plant hormone.
As for techniques for regulating the growth of lawn grasses, it has been reported that benzyladenine has an effect for accelerating the rooting of lawn grasses (Non-patent document 1), that benzyladenine has an effect for accelerating the growth of lawn grasses (Patent document 1), that ethephon (2-chloroethylphosphonic acid) promotes the extension of stolon and increase of the weight in lawn grasses (Non-patent document 2), and that gibberellins and cytokinins can be used for accelerating the growth of lawn grasses (Patent document 2). However, none of these documents describe any techniques for controlling weeds in turf.
As for a technique for controlling weeds, there is a method which involves accelerating the ear emergence of annual bluegrass (Poa annua L.) by application of gibberellin on lawn grasses of a golf course and mowing the ears which have grown taller than the lawn grasses (Patent document 3); in this method, however, there is a problem that the grown ears of annual bluegrass (Poa annua L.) have to be mowed by hand. In addition, it has been reported that annual bluegrass (Poa annua L.) growing among Kentucky bluegrass has slowed growth by treatment with ethephon (Non-patent document 3); and that ethephon inhibits the ear emergence of annual bluegrass (Poa annua L.) growing among bent grass (Non-patent document 4). These methods, however, have the disadvantage that a large quantity of ethephon has to be applied, that is, at a dose of 3.2 kg/hectare for the methods of Non-patent document 3, and 3.8-7.6 kg/hectare for Non-patent document 4. In addition, Non-patent document 4 describes that a large quantity of nitrogen fertilizer has to be applied in order to reduce chemical injury of bent grass.
As mentioned above, though several methods for controlling gramineous weeds such as annual bluegrass (Poa annua L.) growing in turf have been reported, none of them can control these weeds to a satisfactory extent or regulate their growth easily and economically.
Non-patent document 1: Noyaku Binran (Handbook of Agrochemicals), 8th edition, Nobunkyo, 1995
Non-patent document 2: Shibakusa Kenkyu (Study of Lawn Grass), vol. 23, no. 2, p. 5-11 (1995)
Non-patent document 3: J. Am. Soc. Hortic. Sci. (1985), 110(5), 609-611
Non-patent document 4: HortScience (2005), 40(3), 836-838
Patent document 1: JP-A-55-162706
Patent document 2: JP-A-7-82113
Patent document 3: JP-A-61-111626